In-flight refueling (or air-to-air refueling) is an important method for extending the range of aircraft traveling long distances over areas having no feasible landing or refueling points. Although in-flight refueling is a relatively common operation, especially for military aircraft, the aircraft to be refueled (e.g., the receiver aircraft) must be precisely positioned relative to the tanker aircraft in order to provide safe engagement while the fuel is dispensed to the receiver aircraft. The requirement for precise relative spatial positioning of the two rapidly moving aircraft makes in-flight refueling a challenging operation.
There are currently two primary systems for in-flight refueling. One is a hose and drogue system, which includes a refueling hose having a drogue disposed at one end. The hose and drogue are deployed so as to trail behind the tanker aircraft when the aircraft is in flight. The pilot of the receiver aircraft flies the receiver aircraft to intercept and couple with the drogue for refueling.
Another in-flight refueling system is a boom refueling system. The boom refueling system typically includes a rigid boom that extends from the tanker aircraft and includes a probe and nozzle at its distal end. The boom also includes airfoils controlled by a boom operator stationed on the refueling aircraft. The airfoils allow the boom operator to actively maneuver the boom with respect to the receiver aircraft, which flies in a fixed refueling position below and aft of the tanker aircraft.
One drawback with the two refueling arrangements described above is that they tend to be mutually exclusive. The hose and drogue system includes a female receptacle that receives a male probe from the receiver aircraft, while the boom system includes a male probe that is received in a corresponding female receptacle of the receiver aircraft. Accordingly, tanker aircraft equipped with a hose and drogue refueling system are typically unable to supply fuel to a receiver aircraft that is configured to receive fuel from a boom system, and vice versa.
One approach to addressing the foregoing problem is to temporarily attach a “pigtail” to the end of a boom-based probe. The pigtail includes a relatively short, flexible hose segment and a drogue generally similar to a conventional drogue. In operation, a tanker aircraft that is fitted with a conventional refueling boom lands after refueling one or more aircraft that are compatible with the refueling boom. While the tanker aircraft is on the ground, it is outfitted with the removable pigtail. The tanker aircraft then takes off and is available to refuel other receiver aircraft that are compatible only with a hose and drogue system.
One drawback with the foregoing arrangement is that the tanker aircraft must land prior to changing over from a probe refueling system to a hose and drogue refueling system. Another drawback is that the foregoing system is not configured to allow tanker aircraft having a hose and drogue refueling arrangement to change over to a boom and probe refueling arrangement.
An approach to addressing the foregoing drawback is to outfit a tanker aircraft with multiple hoses and drogues, including at least one for generally small aircraft (typically located at the wing of the tanker aircraft), and one for larger aircraft (typically located at the fuselage of the tanker aircraft). One problem with this approach is that it requires several sets of hoses, pumps, reels, fuel routing arrangements and other support equipment, all of which occupy space and payload capacity that might otherwise be available for fuel. Another problem is that this arrangement does not allow a tanker aircraft configured with a boom and probe to refuel aircraft configured for hose and drogue refueling. Accordingly, still another approach to the foregoing problem is to outfit aircraft with both a fuselage-mounted boom and probe and one or more wing-mounted hose and drogue systems. While this approach allows a single tanker aircraft to refuel receiver aircraft having either a hose and drogue compatibility or a boom and probe compatibility, this approach is complicated and heavy, which reduces the operational efficiency of the tanker aircraft.